非晶态金属
无定形固体
铈
材料科学
协调数
玻璃化转变
对分布函数
离域电子
热膨胀
过渡金属
电阻率和电导率
衍射
化学物理
热力学
化学
结晶学
冶金
离子
复合材料
光学
催化作用
生物化学
聚合物
数学
有机化学
数学分析
工程类
电气工程
物理
作者
Zhi Chen,Zhaoyue Sun,Fujun Lan,Xin Zhang,Ziliang Yin,Ye Liu,Zhidan Zeng,Yang Ren,Hongbo Lou,Baolong Shen,Qiaoshi Zeng
摘要
Cerium-based metallic glasses are prototype polyamorphous systems with pressure-induced polyamorphic transitions extensively reported. Cooling typically has a similar effect on materials as compression with regard to reducing volume. However, previous studies show dramatically different behavior of Ce-based metallic glasses between cooling and compression, whose origin remains unclear. Here, using in situ low-temperature synchrotron high-energy x-ray diffraction, the structural evolution of a Ce68Al10Cu20Co2 metallic glass is accurately determined and analyzed by a structure factor and a reduced pair distribution function (PDF) during cooling from 298 to 83 K. An unusually large linear thermal expansion coefficient is revealed, which is associated with both continuous but inconsistent structural changes between the two subpeaks of the first atomic shell in terms of average bond lengths and coordination numbers. These phenomena are suggested to be attributed to a gradual 4f electron delocalization of only a minimal amount (∼2.6% at 83 K) of Ce atoms by quantitative analysis of the PDF data. However, a previously expected global polymorphic transition from a low-density amorphous state to a high-density amorphous state with an abrupt volume collapse is not observed. Moreover, electrical resistivity also shows a continuous increase during cooling without any sharp change. It is clarified that cryogenic temperatures could facilitate but are not powerful enough alone to trigger a global polymorphic transition in the Ce68Al10Cu20Co2 metallic glass, suggesting a wide distribution of its local atomic environment.
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